A friend explained it to me (I have trouble understanding the concept as well) - yes I've read the details on the site and all the posts on here

let's take a simple scene where a man stands with his hands by his side and then scratches his head. With 35mm we would have a series of sequential shots of the hand going up and down - complete images 1 through 50. With video we would have the same but the images would be interlaced - half images.

With HDV we are trying to fit a lot of information on an existing media (miniDV) and so instead of complete images 1 through 50 we have a complete image 1 and then we only record the data that has changed (the moving hand) and then we have a complete image again at frame 8 or 15 (I'm not sure of the figures).

If you want to look at frame 3 or 6, your NLE has to recreate that frame from the complete frame plus all the changes. Cineform does that before you start the editing process.

there is also the fact that m2v or mpeg files are compressed files and editing direct from them means you lose even more data when you've finished. Cineform creates a files that 'looks' as good as the original in an AVI format which is better for editing.

This may be completely wrong, absolute rubbish and totally untrue but it made sense to me so I bought the program.

"If you are intending to edit HDV on CS3, AspectHD has at least 3 cool features. First, as you transfer your footage from your camera to computer you can set it up so that your footage is converted on the fly from MPEG2 to a CFHD-codec avi file. These avi files require much less grunt from your computer to process, you can edit and re-edit them multiple times without losing much quality, and they are fast to render into other formats (like DVD-mpeg, or flash, or whatever).

In comparison, editing raw HDV files on CS3 will feel sluggish, render times are longer, and if you edit them repeatedly their quality deteriorates fast.

Second, the Cineform codec gives you a high-quality way to store your edited footage with fairly modest file sizes - prior to Cineform a lot of people used uncompressed or huffyuv codecs to store stuff, and those files were huge! So if you are creating DVDs now, you can go back and create BluRay disks later once you have the gear.

Third, cineform files play nicely with many other software applications - most anything that accepts avi files can play or edit them. And Cineform provides a little app called HDLink that will losslessly rewrap them as movs for software that wants movs rather than avis (e.g. if you need to move back and forwards between Mac and PC)."

Ding - OK elevator doors opening so I'll stop there. If you had been going up another floor I would have mentioned:

4) AspectHD enables quite a few real-time effects and transitions (color correction, fades, dissolves etc) so you can preview them without rendering;

5) HDLink can do cool stuff on the fly like deinterlacing, framerate changes, and pulldowns; and

6)there's a tempting upgrade pathway if you ever want to get into really high-quality stuff, like 10-bit processing, 2K and 4K workflows ... yadayada.

I'll try a shorter version of Graham's explanation.
HDV( MPEG2) is packaged in groups of 15 frames so that anything other than the first needs the information from the others to assemble the picture. It uses less information to record.
Cineform and other intermediates recreates the individual frames with all their information for easy editing and processing. IT consequently creates a bigger file depending on settings but normally 4 or 5 times the files size of HDV.
Benefit is less load on the PC for editing( doesn't have to decode 15 GOP as well as manipulate effects required). Cons are bigger files sizes and consequently need for faster throughput from drives while editing.

Gee it feels like I just bought a better camera, but it's the same one I had before I started using the Cineform software. Now my files have all the frame information I want, more color resolution, and I can edit, re-edit and pass the files from one application to another with no visible loss of details and all the rich colors and tonalities that I've been trying to pull out of that scene.

Simon, I think you would want to be using Neo HDV. Vegas has Cineform codecs, but these only function within Vegas. If you add Neo HDV, then you can access higher quality versions of Cineform files with Vegas or any other software that uses AVI files.

If cineform converts any camera format (1080i, 720p, 1080p?) into it's intermediary format so I can edit them all together, then when I'm finished editing do I get to decide which format to "output" onto videotape?

If so , then I shoot my fast action motion scenes in 720p, and my beautiful tableaux scenes in 1080i, and then edit everything together and get the best of both worlds?

Ahh, but then I suppose if I export to 1080i, my fast action motion scenes will still show motion distortion. But at least I'd have a choice at the end as to which format serves the majority of my footage best!